The invention relates to a closure tape for an absorbent article, particularly for a disposable diaper, for fastening of the article on the body of a person, said closure tape being attachable to the absorbent article through one of its end portions and comprising a backing, a fastening means and an elastic sheet to render the closure tape elastically stretchable. The invention furthermore relates to a prelaminated closure tape in a stable roll from which the closure tape can be cut.
Absorbent articles such as disposable diapers are provided with closure tapes which are anchored to the absorbent article through one of its end portions by means of, for example, a pressure-sensitive adhesive layer. The opposite end portion of the closure tape comprises a fastening means to close the absorbent article around the wearer""s body and fasten the absorbent article on the body. Among these closure tapes, there have also been described elastically stretchable tapes to improve the fit and the comfort of the absorbent article.
U.S. Pat. No. 3,800,796 discloses a diaper with semi-elastic strip fasteners having a freely extensible elastic central segment and two non-extensible inelastic terminal segments. A similar construction is also described in EP 0,249,073 wherein the boundary regions between the elastic middle portion and the two non-elastic end portions are formed by melt-extrusion of both or either of the elastic material and the non-elastic material in order to provide integral bonding between the segments. EP 0,247,855 provides a composite prelaminated closure tape which can be dispensed from a stable roll form to provide a closure with a central elastomeric sheet. The prelaminated closure tape is securely fastened to the inside and outside surface of one edge of the diaper. The attached closure tape comprises a central elastomeric portion and two anchor strips as end portions.
The elastically stretchable closure tapes described in U.S. Pat. No. 3,800,796, EP 0,249,073 and EP 0,247,855 comprise an elastic middle portion between two non-elastic end portions or anchor strips. While these closure tapes are useful and of commercial importance they are sometimes disadvantageous in that the method of preparing them is relatively complicated and requires secure bonding of the tape segments.
In another group of references the elastically stretchable closure tape comprises an elastic backing. U.S. Pat. No. 4,063,559 discloses a disposable diaper with a closure tape having an extendible or stretchable backing made from a variety of materials comprising, for example, plasticized polyvinyl chloride films, polyolefin films, polyurethane films, vinyl chloride and vinylidene chloride copolymer films, rubber hydrochloride films, polyamide films or elastomeric films derived from styrene-butadiene or styrene-isoprene block copolymers. The backing bears an adhesive layer with a partible protective cover means on top of it. The protective cover is substantially coextensive with the adhesive coating when the closure tape is in a non-extended storage position, but is parted when the closure tape is stretched into the working position, thereby making portions of the adhesive coating available for use in securing the diaper to the body of an infant. The protective cover means may comprise discontinuous slits which form discrete apertures when stretched. Alternatively, the protective cover means may be an embossed, rupturable thermoplastic web or a unitary web provided with spaced, weakened regions which rupture when the web is stretched.
EP 0,191,355 discloses a fastening tape for a disposable diaper comprising a base tape or a backing carrying thereon an adhesive layer wherein the backing when subjected to stress (tension) and subsequently strain (elongation), shows a hysteresis curve with a hysteresis loss ratio of between 20 to 80%. The backing may include a plurality of weakened areas in various geometrical shapes (see FIGS. 9-12), among them discontinuous slits extending orthogonally with respect to the long axis of the backing (cross direction). In an alternative embodiment, EP 0,191,355 describes a fastening tape having two non-elastic end portions and an elastic middle portion made from an elastic material having a hysteresis loss ratio of between 20 to 80%. Using closure tapes with elastically stretchable backings is sometimes disadvantageous because the closure tape which is attached to the diaper may exhibit an insufficient rigidity orthogonal to the long axis of the backing (machine direction) and be floppy.
EP 0,704,196 describes a fastening tape having a stretchable elastic portion which is a sandwich structure of a stretchable elastic tape and a non-elastic backing whereby the elastic tape is secured to the non-elastic backing at least at both ends thereof to bridge a section of the backing which is longer than the elastic tape section and may assume, for example, a zigzag folding shape. If the fastening tape is stretched into a predetermined position, the elastic tape extends and the zigzag-form of the non-elastic backing disappears. The rigidity of the fastening tape in machine direction in the relaxed state is determined by the non-elastic backing. In the construction of EP 0,704,196 it is sometimes difficult to reliably adhere the elastic tape to the zigzag-shaped non-elastic backing.
U.S. Pat. No. 4,834,820 discloses a closure tape having an elastic sheet extending over the whole length of the closure tape and a non-flexible retaining sheet partly bonded to the flexible sheet. The retaining sheet may comprise one or two cut-off grooves. The retaining sheet is ripped apart along the cut-off grooves thus rendering the closure tape elastic, and the central portion of the retaining sheet may be removed in one embodiment (FIGS. 4 and 5). The closure tape is claimed not to interfere with the abdominal respiration of the baby after wearing and eliminates the need for peeling off the tape for checking for urination and stool.
U.S. Pat. No. 4,795,456 discloses an extensible diaper closure tape which comprises an extensible layer 4 uninterruptedly extending over the whole length of the tape. The extensible layer bears on one side a carrier web layer with an unwind release coating the carrier web layer being attached to the flexible layer with a first adhesive layer. The carrier web layer exhibits one or more incisions, and the adhesive layer beneath the slits may or may be not be removed. The other side of the extensible layer carries a second adhesive layer which may be slitted in the same area where the first adhesive layer on the opposite side of the extensible layer exhibits an incision. A non-extensible layer bearing on the exposed side a third adhesive layer, is attached to the second adhesive layer. The non-extensible layer is permanently adhered to the second adhesive layer in the area from the manufacturer""s end to the incisions, and it is releasably adhered to the second adhesive layer in the area from the user""s end to the incisions. The tape is attached to the outside surface of the diaper with the third adhesive layer at the manufacturer""s end and bent around the edge portion of the diaper thus adhering the user""s end with the third adhesive layer to the inside surface of the diaper prior to use. When deployed, the closure tape opens along the release coating between the second adhesive layer and the non-extensible layer which remains adhered to the edge portion of the diaper. The user""s end which has been rendered flexible by the deployment can be used to secure the diaper to the wearer. The closure tape of U.S. Pat. No. 4,795,456 is non-extensible in the initial state prior to use but rendered extensible on deployment which is advantageous. On the other hand, the closure tape is secured to the outside surface of the diaper only. This peel mode type of attachment offers a relatively low bonding strength and may fail when securing the diaper around the wearer""s body or during use. Prior to deployment, the slits which are in the area where the tape is being bent around the edge portion of the diaper, open at least partly thus rendering the surface of the tape coarse which is less preferred. The slits are furthermore easily contaminated.
Therefore there was a need for an elastically stretchable closure tape which is easy to manufacture and does not exhibit the shortcomings of the closure tapes available in the state of the art or exhibits them to a lower degree only. Other objects of the present invention are evident from the following detailed description of the invention.
The present invention refers to a closure tape 10 for an absorbent article, particularly for a disposable diaper 1, for fastening of the article on the body of a person, the closure tape 10 being attachable to the outside surface 3 of the diaper 1 through one of its end portions 17 and comprising a backing 11 bearing a continuous or discontinuous adhesive layer 12, a fastening means 15 and a stretchable elastic sheet 13, the backing 11 being essentially non-elastic and/or non-extensible, the support sheet 20 comprising the backing 11 and the continuous or discontinuous adhesive layer 12 exhibiting one or more incisions 14 in the area of the elastic sheet with at least one of the incisions extending in the machine direction (direction orthogonal to the long axis of the closure tape) over the full width of the backing 11, and the end portion 17 being separated from the incision 14 closest to 10 the end portion 17, by a sufficiently large distance 22 to prevent the incisions 14 essentially from opening when attaching the end portion 17 to the outside surface 3 of the diaper 1 and bending the remaining part of the closure tape 10 to contact the inside surface 2 of the diaper 1.
The invention furthermore refers to a prelaninated closure tape in a stable roll from which the closure tape 10 according to the invention can be cut, and to an absorbent article, in particular a diaper 1, comprising a closure tape according to the invention.